Recently, a wireless power transmission technique using an electromagnetic induction interaction between a primary (power transmitting) coil and a secondary (power receiving) coil that face each other to transmit power without a physical contact, such as a cable, has been drawing attention, and the extensive use thereof in a power supply apparatus for charging a secondary battery mounted on an electric vehicle (EV) or a hybrid electric vehicle (HEV) is anticipated.
Such a wireless power transmission technique enables power transmission without a physical contact, and therefore, is expected to be applied to an external power supply apparatus for a travelling electric vehicle or hybrid electric vehicle. For example, Patent Literature 1 discloses a technique for efficiently transmitting power to an on-vehicle power storage apparatus from a power supply apparatus external to the vehicle while the vehicle is traveling by using a plurality of secondary resonant coils provided to the moving body.
Meanwhile, in a case of applying the wireless power transmission technique to a charging apparatus in a power electronics apparatus, such as an electric vehicle, transmission of a large amount of power is required, and therefore, a large current needs to be supplied to a coil. Accordingly, the intensity of a leakage magnetic field formed in a location away from the coil is high, which might cause an electromagnetic disturbance that adversely affects nearby electronic devices and so on.
On the other hand, Patent Literature 2 proposes a noncontact power transmission apparatus including an electromagnetic shielding member that opens only in one direction so as to enable power transmission from a power transmitting resonator to a power receiving resonator, the power transmitting resonator being housed inside the electromagnetic shielding member.